Optical spectroscopy is currently used for detecting oil or grease contamination in water. This requires a window that inevitably becomes dirty, limiting the period between which intervention into the instrument is required. Direct detection (measurement performed directly on the contaminated water) currently employs either droplet counting or UV detection. Droplet counting will detect only free oil in droplet form (i.e. not that dissolved into the water) whilst UV will only detect aromatic content of the oil (and thus to determine ppm oil contamination, an aromatic/aliphatic ratio must be assumed for the oil).
Indirect detection techniques employ a solvent (e.g. cyclohexane) to extract (and hence concentrate) the oil contamination in the water. This solvent can then be analysed using IR to determine the oil contamination level. The method however relies on complete separation of the solvent and the water—this is particularly difficult to ensure, particularly when the water contains dispersant/surfactant chemicals. The technique requires substantial manual handling in the form of liquid/liquid extraction. In addition, small amounts of residual water can significantly degrade the quality of the measurement.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.